Engine build for historic rally 998

[camelotr]

Dear Friends! I would like to ask You opinions on an ongoing mini project.

I am building a 998 engine for a historic rally mini.

Intended spec:
- forged pistons
- 11:1 CR
- 12G940 head
- MG metro camshaft
- S forged rockers with fix spacers
- MED crankshaft x drilled

I just got the block back from the machine workshop, and measured it.

Piston-bore 0.06mm with acceptable honing pattern, although some remains of the boring still present unfortunatly.

Crankshaft main bearings: 1-0.05mm 2-0.055mm 3-0.065mm (???) measured with plastigauge.
rod bearings: 0.05mm each

Crankshaft axial free play: 0.11mm

Piston ring gaps: 1 - 0.45, 0.45
2 - 0.4, 0.4
3 - 0.4, 0.45
4 - 0.4, 0.45

Oil controls are between 0.6-0.8

Ideas?

Edited by camelotr on Wednesday 18th January 17:20

[mtrehy]

Hey,

I wouldn't want to take much more out of the bore with the hone if you are already at 0.06. You'll need to use your own judgement before you put the hone down it - where exactly in the bore are the left over machining marks? Also have you checked the bore size in several different locations?

I'd be unhappy to get a block back from the machine shop and see anything other than a perfect cross-hatch. It's not that difficult a procedure.

Personally I wouldn't use plastigauge - you need bore gauge and micrometer to do that accurately which presumably you have if you are measuring the bore?

There can't be much left to learn about these engines which aren't covered in detail in Vizard's A-Series books.

Good luck.

[Cooperman]

The 998 will rev well, so you could go a bit 'hotter' with the cam. I ran a 286 in a 998 historic rally car with a straight-cut close-ratio gearbox and a 4.1:1 final drive. Carbs were twin HS2 with a 3-into-1 Cooper exhaust manifold. It gave 74 bhp at the flywheel 6500 rpm.

[camelotr]

I borrowed a point-end caliper today to check the clearances at tzhe crankshaft. It is quite close to the numbers measured with the plastigauge: Main 1 - 0.04 2 - 0.05 3- 0.06+.

[camelotr]

I did not started this engine build from 0, but rather I bought a 1-race old Mini se7en race engine built by a recognized specialist. The MG cam is a mandatory cam of that race afaik. Theese engines rev up to 8K. The pockets in the block do not let much more lift I assume.

BTW the cam was set by the builder to 103 degrees. Factory recomendation is significantly more for this cam at 107.5 degrees. Shall I keep this timing, or is there any reason to alter it soo much?

Edited by camelotr on Wednesday 18th January 17:26

Edited by camelotr on Wednesday 18th January 17:27

[camelotr]

I had to move the engine into a pre A+ block. Most of the features of the A+ block were copied like the pockets, water gallery alterations, deck height etc, but I found that the gearbox to block bolts were impoved from 1/4 to 3/8 thickness. I never heard that A series engines are proen to this kind of failure. Is it worth to go for theese changes also?

[camelotr]

The boring marks in the block are very faint. I am also not happy with them, but I am not too much worried either. Measurements are the same in the whole lenght of the bore n/s and e/w also.